This entry asks a yes/no question, when there is no yes/no answer. If you read the TechCrunch comments on FreeBase, there are a couple of people who say they had the exact same idea -- one even reserved "ifreebase.com." The idea is definitely not new. Facebook wasn't entirely novel either. There are a lot of factors that can make a good idea unprofitable, or a so-so idea a big hit (who knew what AJAX was before it was called "AJAX"?). So, yes, your idea may be stolen if it's good. If your idea is obvious, there is a chance that people are just too lazy to implement it. The only way to win in either case, is to work damn hard on your idea until fruitition.